Hitler believed he will eventually win WW2
The premise of your question is wrong. Hitler never wanted a World War, he had already experienced losing a two front world war once and by the time they started to implement the death camps for real, it was pretty clear that they would likely lose.
Did they just give up when it did not look good? Certainly not. Did anybody talk about it not looking good? Uh, certainly not, that would have been "defeatism" and punishable by death. But don't assume people were blind to the facts just because they did not roll over and accept the inevitable.
For a closer look, I recommend higher ranking military commanders talking in captivity (and being wiretapped) and especially higher ranking military in private conversations. In the middle of the Barbarossa campaign, months from the winter debacle, General Heinrici wrote to his wife, which properties to sell and which to keep, because some would lose in value quickly after allied bombers would be in reach. People were not blind to the fact that Barbarossa had been a gamble and it had been lost.
So Hitler had no grand plans for world domination. We don't know whether he actually believed they would win the war they had on their hands, but people with some realistic viewpoints did not and there is no reason to believe Hitler did not know this. The fact that he did propagate the "Endsieg" until the very end is hardly surprising given the fact that defeat meant his certain personal death. You don't give up fights that end with your own death, no matter how slim the chances. And you certainly don't tell your team all is lost if you want them to fight for you.
So the more realistic leaders did not believe it would all turn out well and others were consumed by their hatred anyway.